You can insert images in the shapes of RadDiagram by creating shape templates as described in the following help article: http://www.telerik.com/help/aspnet-ajax/diagram-shape-templates.html
Please check also the sample that I attached in the other forum thread, in which you posted: http://www.telerik.com/forums/can-we-use-a-custom-shape-%28i-e-image%29-in-the-diagram
I would suggest using only one support ticket/forum thread per case when reporting problems in the future. This will help with investigating the issue, because all of the information about the scenario will be in one place and easier to track.
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